Making changes to the base weapon of a magic weapon

Question

How able are you to modify a weapon after it has been created?

When it comes to magical abilities that use up the enhancement bonus, you are only able to ADD to the existing item. You are unable to replace them (except in rare cases like upgrading flaming to flaming burst). So you would be unable to have a flaming weapon, become a shocking weapon instead.

The above example doesnt change the weapons purpose or materials. Altering Existing Magic Items (scroll up)

The standard rules don't allow item creation feats to alter the physical nature of an item, its default size, its shape, or its magical properties. For example, there is no mechanism for using crafting feats to change a steel + 1 longsword into an adamantine + 1 longsword , a Large + 1 chain shirt into a Medium + 1 chain shirt , boots of speed into an amulet of speed , or a + 1 unholy longsword into a + 1 flaming shock longsword. Many GMs might decide that these kinds of transformations are impossible, beyond the scope of mortals, or not as cost-efficient as crafting a new item from scratch. Others might allow these sorts of transformations for free or a small surcharge. Keep in mind the following warnings.

So my question is, what about changing a base weapon in a reasonable way? The best example I can use is the longbow, composite. Would you be able to upgrade your +1 longbow, composite (+1) to a +1 longbow, composite (+2)? Is this allowed, or is the area so grey that its a GM decision?

Answer 1

Long story short, you cannot. All ways to "modify" it will also involve permanently removing all magic from the item.

Most magic dispelling effects are temporary. A Disjunction spell will destroy the item completely. And breaking it until all hit points are lost will remove all magic, but the item can be fixed with spells and remain a simple masterwork item, meaning that it's much easier to simply buy another masterwork item.

As for mundane items, you will have to ask your GM, as there are no rules for this on the Craft skill. And most modifications will be a case by case analysis.

Like, attaching a chain to a kama will make a kasurigama, attaching another axe head to a two-handed axe will make a double-axe. If you make a pointy tip with metal, bone or otherwise and tie it on top of a quarterstaff, you could call it a spear. And so on.

But a lot of items will simply not work that way, and each GM/table will have different opinions on each item individually. Like, what is the difference between a composite bow +1 and a composite bow +4? What makes one stronger than the other?

I would say "everything", the craftmanship is completely different, you need a different wood, a different technique, etc. But some other guy might understand more about crafting of bows and say "no, all you have to do is work on it for a little longer and it will be studier". So this will suffer from table variation.

This kind of modification could easily fall under the Repair Item rules, as the base item isn't changed and is simply being modified, and as such:

• Pay 1/5 of the cost of that new item.
• Make a craft check against the same DC to create the new item.
• If you fail by 5 or more, the cost paid in materials is wasted and you must try again.

You might consider the difference between the two items, if they are too different (new item is more expensive than the base item), you might consider that you must make a new item altogether, and use the base item cost as material cost instead.

Answer 2

The closest thing to RAW that allows altering one weapon to another type is adding enchantments:

For Composite bows, look at adding Adaptive For melee weapons, your best bet is Transformative, but that's expensive and doesn't allow you to alter it into a different 'handedness' so you're still out of luck if you want your Longsword to become a Greatsword.

I would venture to say that most GMs would allow house rules using Craft to alter equipment into similar pieces, or finding a Blacksmith willing to do it (although at that point its almost worth selling the item for 1/2 and putting the money toward exactly what you want).